Expected and unexpected behavior of the orientational order and dynamics induced by azobenzene solutes in a nematic

We have explored the changes in the phase stability, orientational order, and dynamics of the nematic 4-cyano-4¢-n-pentylbiphenyl (5CB) doped with either the trans or the cis form of different p-azobenzene derivatives using the ESR spin-probe technique. In particular, we have studied the effects induced by each of the seven nonmesogenic 4-R-phenylazobenzenes (R = H, F, Br, CH3, CF3, On-Bu, Ot-Bu) at 1% and 7% mole fraction on the order parameter and on the shift of the nematic-isotropic transition temperature (TNI), as reported by a nitroxide spin probe, and we have tried to relate them to the solute shape and charge distribution. In all the cases the presence of the azo-derivative causes a depression of TNI, more pronounced for the cis isomers. The dependence of on the reduced temperature T*=T/TNI remains the same as that of pure 5CB in all trans-doped samples at 1% and 7% and decreases only slightly in the cis at 1%. However, we observe different and in some cases large variations (up to 25%) in for the cis at 7%, showing solute effects that go beyond the shift in TNI. Surprisingly enough, even at the highest concentration, the probe dynamics appears to be essentially independent of the nature, the configuration, and the concentration of the different solutes and very similar to that observed in the pure 5CB

O corpo despido pelas práticas de desenhar: dos usos à disciplinarização do desenho

Inserido na problemática de investigação sobre os motivos pelos quais as práticas socioculturais de desenhar teriam adquirido e perdido o estatuto de conteúdo escolar, este artigo tem por objetivo refletir acerca dos diferentes usos dados à prática do desenho do corpo humano em duas atividades específicas: a atividade artística e a atividade médica. Parte-se do pressuposto de que a compreensão de características da vida escolar das práticas de desenhar exige a investigação dessas práticas em espaços não escolares. Como a prática do desenho do corpo tem atravessado os espaços escolares brasileiros, é nosso interesse, portanto, investigar como se pôde formar tal domínio de saber. Nesse sentido, nossa estratégia será analisar que problemáticas permearam tal prática durante o Renascimento, a fim de compreender possíveis implicações filosóficas, conceituais, técnicas e científicas decorrentes de suas diversas significações

Breast cancer "tailored follow-up" in Italian oncology units: a web-based survey

urpose: Breast cancer follow-up procedures after primary treatment are still a controversial issue. Aim of this study was to investigate, through a web-based survey, surveillance methodologies selected by Italian oncologists in everyday clinical practice. Methods: Referents of Italian medical oncology units were invited to participate to the study via e-mail through the SurveyMonkey website. Participants were asked how, in their institution, exams of disease staging and follow-up are planned in asymptomatic women and if surveillance continues beyond the 5th year. Results: Between February and May 2013, 125 out of 233 (53.6%) invited referents of Italian medical oncology units agreed to participate in the survey. Ninety-seven (77.6%) referents state that modalities of breast cancer follow-up are planned according to the risk of disease progression at diagnosis and only 12 (9.6%) oncology units apply the minimal follow-up procedures according to international guidelines. Minimal follow-up is never applied in high risk asymptomatic women. Ninety-eight (78.4%) oncology units continue follow-up in all patients beyond 5 years. Conclusions: Our survey shows that 90.4% of participating Italian oncology units declare they do not apply the minimal breast cancer follow-up procedures after primary treatment in asymptomatic women, as suggested by national and international guidelines. Interestingly, about 80.0% of interviewed referents performs the so called "tailored follow-up", high intensity for high risk, low intensity for low risk patients. There is an urgent need of randomized clinical trials able to determine the effectiveness of risk-based follow-up modalities, their ideal frequency and persistence in time

Synthesis, reactivity, and electronic structure of multifarious, five-membered heteroaryl and heteroaroyl azides

The aim of this account is to review our most important outcomes ― published during the last 30 years ― concerning the azido group that is linked to five-membered heteroaryl and heteroaroyl systems. The main focus of this manuscript is on the \u2018azido transfer\u2019 reaction to heteroaryl azides, and the peculiar thermal and chemical reactivities of these precursor species. In particular, the following topics are considered: (a) the ring cleavage of α-heteroaryl azides to form 4-cyano-1,3-heterodienes, (b) the reactivity of thermally generated β-nitrene, (c) the 1,3- dipolar cycloaddition of the azido group to various terminal or 1,2-disubstituted alkenes or alkynes to form nitrogen-containing biheterocycles, (d) the generation of electrophile nitrenium ions with Lewis acids, (e) the conversion of heteroaroyl azides into isocyanates, and (f) the 1,3- dipolar cycloadditions of heteroaroyl azides with \u2018activated\u2019 olefins. The concurrence and discordance of the thermal and chemical behaviour between heteroaryl azides, and the related substituted phenyl azides will be critically considered here

Aromaticit\ue0 e composti aromatici

Si descrivono le caratteristiche strutturali ed energetiche unitamente alle tecniche sperimentali spettrocopiche, termiche ed elettroniche impiegate per la classificazione di taluni sistemi organici aromatici (e non)

Explosive nitrogen-containing organic compounds. Molecular intrinsic reactivity (MIR) correlation in high-energy molecular structures.

Molecole contenenti numerosi atomi di azoto costituiscono una classe di composti con elevata densità elettronica ed alto contenuto energetico che possono dare luogo ad esplosione termica generalmente associata a rapida eliminazione di frammenti molecolari gassosi. Moderni metodi d'analisi termica ed il calcolo quantomeccanico possono predire la loro sensitività

The Fascinating Chemistry of α-Haloamides

The aim of this review is to highlight the rich chemistry of α-haloamides originally mainly used to discover new C−N, C−O and C−S bond forming reactions, and later widely employed in C−C cross-coupling reactions with C(sp3), C(sp2) and C(sp) coupling partners. Radical-mediated transformations of α-haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α-halohydroxamate-based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates

Preparation and [2 + 3] cycloaddition of thienyl isocyanates with trimethylsilyl azide: One-pot synthesis of thienyltetrazolin-5-ones

Efforts to prepare thienyl isocyanates by thermal reactions of thenoyl chlorides with trimethylsilyl azide (TMSA) led preferentially to the formation of 1,4-disubstituted tetrazolin-5-ones, arising by interaction of the initially formed thienyl isocyanate with TMSA. In fact, 2-thenoyl chloride and benzo[6]thiophene-2-carbonyl chloride reacted with 1 equiv. TMSA in refluxing carbon tetrachloride to give 1-(2-thienyl or benzo[b]thienyl)-4-(2-thenoyl or benzo[b]thiophenecarbonyl)tetrazolin-5-one 4d, e, whereas 3-thenoyl chloride led to 1-(3-thienyl)-4-trimethylsilyltetrazolin-5-one adduct II which was converted, after hydrolytic desilylation, to 1-(3-thienyl)tetrazolin-5(4H)-one 4c. Similar reactions, carried out with more than two equiv. of TMSA, led in all cases to the formation of the corresponding 1-heteroaryltetrazolin-5-one 4a-c via the corresponding silylated tetrazolin-5-ones II, whereas at room temp. such reactions gave essentially thenoyl azides which, after elimination of the excess TMSA, were thermally converted to the corresponding thienyl isocyanates 3 in fairly good yields

UTILITY OF THE AZIDO-GROUP: ELECTRONIC STRUCTURE AND REACTIVITY OF o-OXOARYLNITRENIUM-BF3 IONS AND 2- (or 5-) AZIDOAZOLES DERIVATIVES

In the last decade, knowledge of the chemistry of N-arylnitrenium ions has advanced significantly and continue to attract attention arising from synthetic, theoretical and biological interest. Here we report the reactions of five 2-oxo arylnitrenium-BF3 ions generated from deactivated 2-oxoazidobenzenes, including 2-azidobenzenecarbaldehyde, 1-(2-azidophenyl)-1-ethanone, (2-azidophenyl) (phenyl)methanone , 2-azidobenzoic acid and 2-azidobenzenecarbonitrile, with Lewis acid BF3\u2022OEt2 in the presence of benzene, as a possible source of 2-anilino-oxobenzenes and/or acridines. Synthesis of azido azoles: According to the proton-lithium (or halogen-lithium) exchange reaction via butyllithium, the metallation of the methylimidazole, the methylpyrazole and the thiazole rings occurs regioselectively at the C-2 (or at C-5 when the position-2 is unavailable) and the resulting 2-(or 5-) heteroaryllithium was employed for the azido transfer protocol with tosyl azide